You should buy a 2 2 GB kit for best results. Otherwise they might not be compatible and you will end up crying and buying another system in case you can't even spot the problem parts
Dinesh you might have possibly figured out by the pricing that DDR2 RAM is obsolete? DDR3 has become mainstream.
Coming to the sticks, here're some cheap options from eBay: http://www.ebay.in/i...a#ht_2065wt_700
http://www.ebay.in/i...8#ht_1137wt_892
I'd advise the Transcend sticks since they have a 3 yr warranty compared to the 1 yr offered by Dynet. It would always be advisable to walk into an outlet and pick one up since eBay charges additional expenses. Just tell them you need a 2GB DDR2 stick rated at 800MHz/PC2-6400.